The 10 Most Bizarrely Interchangeable Celebrities

They say we all have a doppelganger out there somewhere, almost assuredly plotting our downfall. That's why you should always dive tackle and pull at the face of anybody who looks even a little bit like you, just to be safe. That's sound advice, and it applies to the everyman as much as it does to celebrities: Hollywood just isn't big enough for two Bill Paxtons, even if one of them is Bill Pullman. So any day now, expect E! News to report on the impromptu death-match between...

#9 - #10. Mark Wahlberg and Matt Damon

Remember, this isn't just about physical identity. Looking at the pictures, any red-blooded Pats fan could easily spot the differences between these two meat-faced Southies. But there's something in their larger persona that causes your brain to misfire when you try to distinguish one from the other. The world just doesn't need two guys trying and hilariously failing to convince audiences that Bostonians are smarter than you think.

Mark Wahlberg made his fame by rapping and showing his underpants. Despite the extrovert briefs and the ever-present Funky Bunch that still, to this day, follows him everywhere he goes, Mark Wahlberg seems like the more down to earth one. He's also less successful, and generally warrants B-movie roles like The Happening. Matt Damon is the more Hollywood of the two actors: He was, at least briefly, the go-to A-Lister for white guy screen filler. He gets both the high-profile and arthouse roles - he's the guy from Good Will Hunting, after all - and you can apparently ride that cachet for ten years, at least.

So it's quiz time: Who was in the Brothers Grimm, the ill-advised tongue-in-cheek action reboot of a collection of fairy tales? That's straight to video caliber premise, right there. Gotta be Wahlberg.

Now here's where it gets tricky: They're both proud former Bostonians. Two Southie white boys, one trying to hold onto his roots, and one still struggling to overcome some criminal connotations. So which one was in The Departed - the Boston mob flick about both of those things? Oscar quality says Damon; but gritty subject matter says Wahlberg.

#7 - #8. Michael Cera and Jesse Eisenberg

The world does not need two human avatars for the concept of "getting beat up in high school a lot." Yet we have both Michael Cera and Jesse Eisenberg awkwardly pawing at the blouse of Hollywood right now. The physical resemblance is pretty strong here, but both have their flagship roles:

Michael Cera was George Michael in Arrested Development.

Jesse Eisenberg was the kid in Zombieland that everybody thought was Michael Cera.

Nick and Norah's Infinite Playlist? Toss-up. It's romantic and quirky, but also a bit more approachable than Cera's traditional fare. Probably Eisenberg? Nope, Cera with the double fake-out.

Squid and the Whale, the Oscar bait drama about families coping with loss (I assume, even though I've never seen it, because they're friggin' all about families coping with loss). The arthouse vibe screams Cera. But no, it was Eisenberg.

Here's where it gets rough: A coming of age story about foul-mouthed young people dealing with the inevitable separation after school while also struggling to accept personal responsibility?

It's okay to be confused: It was by the same people that did Superbad. They probably meant to cast Cera in the pseudo-sequel, but ran into Eisenberg at the supermarket, accidentally gave him the part, and didn't want to make things awkward when he showed up for filming.

#5 - #6. Natalie Portman and Keira Knightley

Natalie Portman was the little girl from The Professional, who still holds a special place in the hearts of pedophiles everywhere. Keira Knightley was the female lead from Pirates of The Caribbean.

They look a bit alike, sure -- insomuch as, below a certain body weight, all pretty white girls look like Legolas. Plus, they both seem like they're smarter than you, and probably wouldn't let you forget it. There's definitely an aura of similarity there, but there are differences: Portman does the arthouse stuff. She's the cultured Harvard chick, while Knightley is the mainstream Renaissance girl. Portman does the smart films, while Knightley does the old timey blockbusters.

King Arthur? That's Knightley. And you're right! Old timey damsel stuff. She's playing right to casting. So which one was in Thor? Kinda dumb, medieval vibe - Knightley? No, Portman again. Haha, what? Did she lose a bet or something?

Which played the lead in that movie about dominos or whatever? Knightley, right?

Keira Knightley starred as the titular character in Domino, Portman starred in the entirely different, how-could-you-even-get-them-confused, Domino One.

Well, then who was in London Boulevard, the British gangster flick? British says Portman, even though Portman is actually American and Knightley is actually British...I think...probably. It takes place in modern times, at any rate. I'm going Portman. But it is, of course, Keira Knightley, who stars in the film opposite Colin Farell.

I mean Colin Firth.

Shit, I don't know: One of those foreign white dudes that looks like a douchier version of...